WASHINGTON — President Joe Biden decried his predecessor for failing to try and stop last year’s deadly mob attack on the Capitol, saying Monday that “Donald Trump lacked the courage to act” as hours of “medieval hell” unfolded.“Every day we rely on law enforcement to save lives. Then, on Jan. 6, we relied on law enforcement to save our democracy,” Biden said in a prerecorded speech to the National Organization of Black Law Enforcement Executives’ annual conference in …